The present disclosure generally relates to actuators that incrementally provide large displacements and/or rotations to an object, and more particularly, to actuators comprising active materials that incrementally provide large displacements and/or rotations to an object.
Active materials such as shape memory alloys, piezoelectrics, magnetorheological polymers, electroactive polymers, and the like are used as limited displacement type actuators. The use of active material actuators in place of mechanical actuators such as solenoids, servo-motors, and the like, minimizes the complexity associated with these types of actuators. Moreover, these materials generally provide a lightweight alternative, minimize packaging space, and provide lower acoustic outputs during operation. However, because these materials provide limited displacement, they have not found utility in actuators that provide large displacements and/or rotations to an object.
In general, actuation distance of active material based actuators is quite limited, being approximately 0.1% of actuator length with piezoelectric materials, 4% with shape memory alloys and magnetic shape memory alloys, and a few % with magnetorheological polymers. Electroactive polymers offer the potential for large displacements (with some in excess of 100%) but at dramatically lower force levels than piezoelectric materials, SMA's, MSMA's, or other form of magnetostrictive or electrostrictive material. Single actuation cycles produced by the field-induced strain of active materials are thus, except for the case of low actuation forces, themselves quite small. Most approaches for achieving large displacements through field activation of active materials have focused on innovative approaches to packaging long lengths of active materials within small volumes.
Accordingly, it would be desirable to utilize the attendant advantages of active materials in actuators and provide large displacements or rotations to an object.